straight ruler and set square.

The best all-round drawing paper, both for India ink and colored work
has a rough surface; it must be fastened firmly and evenly to the board
by means of thumb tacks; the lines must be light and made with a hard
pencil. Use Higgins' India ink, which dries rapidly.

[Illustration]

We will begin by drawing the center line A' A B; use the point B for the
escape center; place the compass on it and strike G H, the primitive or
geometrical circle of the escape wheel; set the center of the protractor
at B and mark off an angle of 30deg. on each side of the line of centers;
this will give us the angles A B E and A B F together, forming the angle
F B E of 60deg., which represents from lock to lock of the pallets. Since
the chord of the angle of 60deg. is equal to the radius of the circle, this
gives us an easy means of verifying this angle by placing the compass at
the points of intersection of F B and E B with the primitive circle G H;
this distance must be equal to the radius of the circle. At these points
we will construct right angles to E B and F B, thus forming the tangents
C A and D A to the primitive circle G H. These tangents meet on the line
of centers at A, which will be the pallet center. Place the compass at A
and draw the locking circle M N at the points of intersection of E B and
F B with the primitive circle G H. The locking edges of the pallets will
always stand on this circle no matter in what relation the pallets
stand to the wheel. Place the center of the protractor at B and draw the
angle of width of pallets of 6deg.; I B E being for the engaging and J B F
for the disengaging pallet. In the equidistant pallet I B is drawn on
the side towards the center, while J B is drawn further from the center.
If we were drawing a circular pallet, one-half the width of pallets
would be placed on each side of E B and F B. At the points of
intersection of I B and J B with the primitive circle G H we draw the
path O for the discharging edge of the engaging and P for that of the
disengaging pallet. The total lock being 1 3/4deg., we construct V' A at
this angle from C A; the point of intersection of V' A with the locking
circle M N, is the position of the locking corner of the engaging
pallet. The pallet having 12deg. draw when locked we place the center of
the protractor on this corner and draw the angle Q M E. Q M will be the
locking face of the engaging pallet. If the face of the pallet w